Common : Matrices as Lenses upon Graphs

Adjacency List

• X : single-column
• Y : node-pair list -> fairly dense

Adjacency Matrix

• X : node list
• Y : node list
• Z : edge count -> a sparse matrix

Incident Matrix 

• X : edge list
• Y : node list
• Z : properties of edges, e.g. weight -> a sparse matrix

Degree Matrix

• X : node list
• Y : node list
• Z : degree of each edge -> a diagonal matrix

Laplacian Matrix

• [ Degree Matrix ] minus [ Adjacency Matrix ]